Discharge tube electrode



Aug. 25, 1931.

F. HoTcHNER 1,820,392

DI SCHARGE TUBE ELECTRQDE Filed March `25. 1929 IN VE/VTOR vus Patented Aug. 25, 1931 UNITED STATES FRED HOTCHNEB, Ol' LOB ANGELES, CALIFORNIA I mscnandn 'ruim nnc'raonn Application l'ed Inch 25, 1989. Serialv No. 349,647.

This invention relates to a discharge tube electrode for va or electric devices or vacuous electric devices in which electrodes hav- .ing the characteristics hereunder outlined are useful.

In my Patent No. 1,789,901- and in other previously filed copending ya plications I have disclosed several types o electrodes in which the 'discharge originates on the inside surface of a hollow cylinder and passes thru a restricted o ening into the main discharge column. or the guidance of those Y skilledz in the art I have advanced a theory of the operation of the device. It vis my theory that the ositive ion bombardment heretofore consi ered an essential part of the mechanism of emission is reduced to a very lowvalue in my invention and that adequate emission is secured thru electric forces. However, thetheor will for a longtime be controversial, an I do not limit my invention by the theory advanced in the previous disclosures or by the additional theories advanced herein. It is to be understood that this is for the guidance of those skilled in the art and that the only limitations tobe placed upon this invention are .those of the prior art and the appended claims.

In one previous disclosure I have explained that if the protecting shield which provides the restricted o ening thrudieleetrie material thru which t edischarge passes is so made that the opening is of capillary dimensions some very surprising and highly useful results are secured. The present invention provides that this capillary passage be at least artly thru the enclosing metal structure within which the discharge originates. Additional advantages are secured by so designing the electrode.

The primary object of this improvement is to provide for the direction of the electric force between `the positive column region of the tube andthe emission surfaces accurately thru the capillary in the dielectric shield thereby relieving the dielectric material around the orifice of all unnecessary electric strain. Certain mechanical improvements are also made to this end.

The discovery has been made that a capillary opening of the nature disclosed will automatically maintain itselfopen and at the correct diameter. This is an altogether novel-mechanism and not at all what might be 'expected from any information of the prior art. A demonstration ofthe action can only be made when certain rigid requirements are met and it is therefore easily understood why this phenomena has escaped previous notice.

As to my theory of the action of this device, I will point, outthat there is always some evaporation, however minute, of the material of .the electrode.y By the term evaporation I mean to include what is sometimes called sputtering of the elect-rode material. In `the course of time a deposit will appear at some place of the evaporated material. I believe that the physical action in the conducting medium in the capillary passage is such that if deposition takes place there that it is automatically stopped at a certain point. It has been found by experience that the transportation of evaporated material thru a small capillary such as I use can only take place under abnormal conditions, and it might therefore be inferred that a capillary of this nature will automatically size itself. When the necessary conditions are observed it has been found that such is the` case. The essential conditiQns from the data now available appear to be these; that the passage thru thel dielectric and conducting pasage be continuous, v

without any space between the shield and the metal (such as might be allowed for expansion), that there be no sharp corners on the metal to which the discharge can become concentrated, and that the capillary be suiiiciently small at the start to prevent any considerable transportation ofmaterial thru the orifice and the depositionthereof on the outside. Other conditions obvious to one skilled in the art are naturally to be observed in addition. One of the objects of this invention therefore is to provide acapillary of the nature shown that will automatically c lose itself to a dimension small enough to prevent any transportation of evaporated material from the electrode.

, cylinder.

Another improvement of considerable importance has been made. By providing for an opening out of the electrode chamber of extremely small section, it is possible to make the chamber in the -form of a s here instead of a cylinder. The object of t is is to provide for a uniform electric force over practically the entire emission surface and to eliminate the-movement of ions alongthe axis of the electrode as can take place 1n a The disturbance, if any, caused by the opening out of the chamber is very slight and it has been found that the `process of evaporation and deposition automatically corrects this condition so far as practical .operation is concerned. j

It will be understood that the discharge can not take place inside of the capillary under normal operating conditions. Other objects of the invention will be ap arent to those skilled in the art from the ollowing specification.

A further object is to provide a new and very simple method of rotecting the lead in conductor from a discharge. The device here used provides a discharge tight joint which isolates the region behind the electrode from the main portion of the tube. The joint in practice is probably in most cases also as tight and inasmuch as it is necessary t at the gases in the region 'behind the electrode be disposed of in pumping the tube I make use of a further novel device to this end. I have discovered that a verysmall'hole thruthe material of the electrode leading from this space into the chamber within the electrode will permit the complete evacuation of the region behind the electrode and still will ermit little if any discharge taking place rom the exposed metal parts in that region when first starting the tube and none at all after the tube has burned in.

In the drawings, Figure 1 is a sectional view of the present invention as applied to an electrode similar to those shown in the previous disclosures.

Figure 2 is a sectional view of this invention in the form of an electrode in which full utilization is made of the advantages of the capillary passage to affect advantageous j changes in other features of the device.

In the view in Figure 1, numeral 1 indicates the electrode end of a discharge tube in which 2 indicates the reentrant stem having the lead in conductor 3 sealed therein; 4, the electrode proper; and 5, the shield.

The electrode proper 4 has the general shape of a capsule, all sharp corners are eliminated on the inside in order that the discharge may not become concentrated at any particular point. The emission takes place from the inside surface and the discharge passes out thru the capillary opening 6. The opening 6 communicates with the breakinv closed capillary opening 7 in the shield 5. The spring 16 pushes the electrode and the shield up against the protrusion 8 in the Wall of the tube proper. In this instance the lead in'conductor 3 has a bent-over portion 9 which makes a pressure contact with the end 10 of the electrode.

In order to rovide for expansion the electrodeis slight y smaller in outside diameter than the inside of the shield, and the shield likewise has a slight clearance in the tube. A novel device is used to protect the lead in conductor. The technique of forming the protrusion in the tube is given in a previous disclosure and is repeated hereunder as modified by improvements o f this record. The final form of the slope 11 of the protrusion 8 is such that it make intimate contact with the surface 12 of the head 13 of the shield, 5 without fusingthereto.. This contact should preferably be confined to an area close to the apex 14 in order than no strain from expansion will be placed on the tube. The fit should be so intimate that no discharge can pass thru to the lead in wire. I have found that such joints if properly executed. are entirely adequate to prevent a discharge from passing to the lead in wire and tubes so made may be easily manipulated thru the degasifying process without the glass at the joint. I believe this to be an entirely new result in the art and one which is of great value. While in my previously filed application No. 341,320 I have shown' in Figure 2 an internal rotrusion in the wall of the tube against w ich an electrode assembly is made to bear for the purpose of mechanical support I had not discovered that such joints could be so improved as to be entirely adequate of themselves to stop the discharge and provided for that purpose a body of porous material between the lead in Wire and the mainchamber of the tube: In order that the region behind the electrode can be freed of gases during the pumping process, a lcapillary opening 15 of extremely small cross-section is provided thru the wall of the electrode. Experimental evidence has shown that this passage will notfrom a practical point of View 'cause sufficient discharge to take place from behind` the electrode to cause any trouble. In operation it often becomes u The inctioning of the capillary 6 has developed very satisfactory features of operation.. The discharge takes lace from the inside surfaces of the capsu e and passes out thru the capillary freely Without closing up the capillary as long as the outside of the capillary opening is well protected from discharge. It is essential that the openings thru the metal and the shield fit together well Without any edge or point to which the 4 discharge can become concentrated and start ,essential that the curves o high .meitin a destructive process. It appears also to be the 'surfaces in contact with the discharge be smooth and re lar and conform to natural lines of flow. n the fabrication of the assembly, the lead in conductor is' made u in the stem in the4 usual manner andseal in the end of a `short piece of lead'glass tube.. The shield and `the lelectrode and spring are placed in the tube .from the open end. The shield isl made of material, such as lPyrexglass, of a 'point compared with lead glass. Ama e tool is introduced in the tube from the open end and the loose partsare depressed until the desired ,compression is .placed on'the spring. The :glass of the tube aroundtheregion of thedesired, protrusiony ments in the design. The electrode proper 20 is in the form of a hollow sphere. This provides for a nearly uniform electric force over the entire active surface. 'It also reduces further the movement of positive ions as com ared with the hollow cylindrical type o electrode. With the .cylindrical electrode there is a component parallel -with the axes of the cylinder which vresults yin a certain ,amount of disintegration at the end'of --the cylinder.

` The shield-21 is made with freely flowing lines in order that the ,-fmaterial may be easi.ly,rn. anifpulated yin manufacturing the same and "finished accurately to the desired shape. Itis to be noted that when the shield is made from material such as glassy that the shape of the finished shield is very close to-that which is naturally taken by a piece of heated glasstube ina semi-fluid state. It is thus -possible to make the shield of very high melting point material and manipulate it :into final shape with little effort. The

bulbulous end 22 of the shield fits into the ring depression 23. in,the outside ofthe` electrode around the openin "The, feather edge 24.of-.the capillary tu thus runs off into a natural intimate contact with the passage thru the shield. The shapes thus givenl The method of forming the protrusion25 in this case is similar to that given above,

`there being` an accumulation of glass brought about in the region of the protrusion. Ity will be noticed that the shape assiv ned to the tube at this oint is such -as to al ow the material tol coo without internal strains. An evenly expanding passage is provided for the dischar e to follow between the capilla and the. tu pro r.

The met od features herembefore disclosed are not claimed in this. application but are claimed in my tion Serial No. 528,833.

The electrode is. provided with a capillary opening 31 for the purpose of providing an escape for the gas behind the electrode.

The s ring`26 is made in the form of a' helix, so

the .wide endbearing on the glass at the en d of the' stem 27, and the narrow end bearing on the electrode. The lead inconductor 28 has a slack loop 29 and the end 30 is pinched onto the sprin to insure a good' contact.

The electr es of the present invention are characterized by the fact that'tlie capillary orifice is interposed between the "Fara day ldark s ace region and the' emission surface of t e electrode. To'tl.is Iascr'ihepartially the different .behavior "of thefdi's'.l charge 1n passing thru the orifice Vof my' device andthe' reportedfbehavior fof dischargespassng t ru orifice's'inter osed fin thepositivc column proper.- "The"ejectrodesY of my ydevice do not evidence arectifying action and do not appear to developany unusual heating effect.

`It is preferred that the capillar portionq of the orifice be veryshort andt at from the narrowest point it open upl rapidly into the electrode chamber and into the main copendingfapplica! 75 chamber of the tube and' that the walls ofv I the passages follow natural lines ogfzflow' The expression natural lines of flow' in a* generic sense applies to' lines of easy-curvature leading to and away from the narrowest oint of the orifice much asv lines would be rawn to provide the bestpaage thru an orifice for afiowing b odyi'of fluid'. 'While' there is an enormous difference in the ph I'sical nature of a fiowingbody and the ow of current by ionization thru a stationary body I have discovered that for some still unknown reason improved results vcan be secured inl-the latter case by designing the walls of passages in the manner described. The term ionization conductor as herein used refers to. any medium in which rad-iation is generated by ionization caused by vthe flow ofl an electric current thenethru. Typical of such mediums are bodies ofthe noble gases at low pressure or the vapors of metals such as mercury. The various features ofthe inventionI-believe to be all new either as used separately or in combinationand have manyl pos- -sible applications in ...discharge tube devices. The invention is not limited to the particular embodiment shown nor to devices inyil cluding all of the illustrated features but may on the contrary be variously embodied singly or in roups in various types of dis- 'char tube evices within the purview of the ollowing claims. I

Having thus described my invention, what I claim is:

1. In a. discharge tube, a hollow electrode from the insidesurface of which the emis sion takes place and a passageof capillary cross-sectional dimension thru the wall of said electrode/thru which the discharge .passes into the tube proper.

2. In a discharge tube, a hollow electrode, the inside surfaces of which are of conducting material, and a discharge passage from the inside of said electrode to the discharge column proper, the walls of said passage being of conductin material and in contact with the aforesai inside surfaces of said electrode, the cross section of said passage being reduced to a diameter suiliciently small to prevent a discharge taking place from the wa ls thereof without preventing the assage of a dischar e therethru to the vc amber within said e ectrode.

3. In a discharge tube, a hollow electrode from the inside surface of which the emission takes place, and a passage of capillary cross-sectional dimension thru the material of the wall of said electrode thru which the discharge passes into the tube proper and a shield of dielectric material having a like passage which forms a continuation of the rst mentioned passage, said shield being positioned to protect the material of said electrode at the end of the first said assage from the action of the discharge an direct the discharge into said passage.

4. In a discharge tube, a hollow electrode, from the inside surface of which the emission takes place, a passage of capillary crosssectional dimension thru the material of the wall of said electrode, a shield of dielectric material having a passage of like dimensions said shield directly abutting the said electrode, said passa e formin a continuous passa e for the discharge rom the inside of said electrode to the discharge column proper, the curvature of the walls of said assages being such as to follow natural lines of flow.

5. In a discharge tube, a hollow spherical electrode from the inside surface of which the emission takes place, a passage of capillary cross-sectional dimension thru which the dischar e passes into the tube proper and dielectric sielding means outside said electrode to direct the discharge thru said passage and prevent the discharge from attacking the outside surfaces of said electrode.

6. In a discharge tube, a hollow electrode, an opening thru the wall of said electrode, the size of said opening being in the order of 65 a capillary passage, a shield of dielectric material, an opening thru said shield of a size in the order of 'a capillary passage, said electrode and said shield being so fashioned and assembled with relation to each other and theenvelope of said tube that the both said'A openings are in direct communication with each other and the discharge in the main ,discharge chamber of the said tube is prevented by said shield from reaching any portion of said electrode except the inside sur-f faces of said electrode b way of the said lopenings in said electro e and said shield.

7. In a discharge tube, an elongated tubular envelope, an inwardly extending protrusion formed from the material of the wall of said tube and comprising a part thereof, an electrode assembly in said tube positioned in the portion of said tube with respect to said protrusion distant from the main discharge column portion of said tube, a portion of' 'said electrode assembly bearing a ainst the said protrusion and forming a f ischargetight joint therewith.

8. In a discharge tube, an elongated tubular envelope, an inwardly extending pro` trusion formed from the material ot the wall of said tube and comprising a part thereof,

an electrode assembly in said tube positioned in the portion of said tube with respect to said protrusion distant from the main dis-I charge column portion of said tube, a portion of said electrode assembly bearing a ainst the said protrusion and forming a discharge-tight joint therewith, and a passage thru said electrode assembly providing communication between the main chamber of said tube and the region behind said electrode the size of said passage being sufficiently small to prevent a material discharge taki-ng place from the exposed metal parts inc' the last said region.

9. In a discharge tube, a hollow electrode from the inside surface of which the emission takes place, and a passage of capillary cross-sectional dimension thru the wall off said electrode thru which the discharge passes into the discharge tube proper, all of the surfaces inside of said electrode being rounded and virtually free from corners.

10. In a discharge tube, an envelope, an. ionization conductor therein, a body of conducting material within said envelope, and a passage thru said bod)1 of conducting material thru which the discharge passes, the

dimensions of said passage being such that' no emission takes place from the walls of said passage.

11. In a discharge tube, an elongated tubular envelope, an inwardly extending protrusion formed from the material of the wall' of said tube and comprising a part thereof, an electrode assembly in said tube positioned in the portion of said tube with respect to said protrusion distant from the main discharge column portion of said tube, a porido lion of said electrode assembly bearing against the said protrusion and forminlr a discharge-tight joint therewith, a lea -in conductor sealed` thru said envelope at a point in the envelope behind said electrode with respect to said protrusion, means to press said electrode assembly againstsaid protrusion, and a passage thru said electrode assembly providing communication between the main chamber of the said tube and the region behind said electrode.

12. In a discharge tube, a cylindrical shield of ydielectric material, one end of said shield being formed into practically a closure for said cylinder, there remaining an opening of practically capillary dimensions thru said closure at or near the axis of said` cylinder, and a hollow electrode having an opening of like dimensions positioned within said shield, both of said openings being in direct communication.

13. The method ofpreventing the migration of evaporated material from an electrode in a discharge tube, which consists in passing the discharge thru a passage of capillarycross-sectional dimension formed thru the material of the wall of said electrode.

14. The method of preventing the migration et evaporated material from an electrode in a discharge tube, which consists in passing said discharge thru a capillary passage formed thru the material of the wall of said electrode.

15. In a discharge tube, a shield of dielectric material, a passage'of capillary dimensions thru said shield, the mater1al around said passage following easily curved lines, and a hollow electrode having an opening of capillary dimensions, the material of said electrode around said passage running off into the said passage thru said shield forming a continuous passage thru the Wall of said electrode and thru said shield.

16. In a discharge tube, an envelope of vitreous material, a member within said envelope of dielectric material forming a discharge barrier between two regions Within said tube, said member and said envelope being joined together without fusion in a joint suiiiciently intimate to prevent the passage of a dischar e therebetween, the entire contacting area 0% being concaved towards the contacting portion of said barrier member, and means to press said barrier member into said joint.

17. In a discharge tube, an envelope of vitreous material, and a member of vitreous material Within said envelope extending between opposite Walls of said envelope and forming a discharge barrier between two regions Within said envelope, said barrier member being formed of material of a lower coeiicient of expansion than the material of said envelope and fitting Within said enthe envelope at said joint v velope and conforming to the contour of the wall thereof with a discharge tight joint.

18. In a discharge tube, an elongated envelope, an electrode assembly near one end of said envelope fitting the walls of said envelope with a discharge tight joint, there being a chamber within said electrode assembly and a capillary passage thru the material of the electrode communicating with thc region behind said electrode assembly thereby providing a passage thru which the atmosphere in said region may be evacuated thru the electrode assembly.

F RED HOTCHN ER. 

